1. Field of Invention
The present disclosure relates to an illumination device. More particularly, the present disclosure relates to a light-emitting diode (LED) dimming circuit of an illumination device.
2. Description of Related Art
As a result of a LED having the advantages of high illumination efficiency, longer service life, etc., various applications of using a white LED as a light source, such as liquid crystal displays and televisions, are more and more popular.
FIG. 1 is a schematic diagram showing a dimming circuit of a LED light source according to a prior art. As shown in FIG. 1, a dimming circuit of a common LED light source uses a two-stage driving circuit. A first-stage AC-to-DC converting module 120 is used to convert an AC voltage provided by mains supply to a DC voltage. A second-stage DC-to-DC converting module 140 converts the aforementioned DC voltage to a driving voltage required by a LED module 160. For achieving the purpose of the dimming control, the second-stage DC-to-DC converting module 140 is adjusted by an external dimming control signal Vdimming in the dimming circuit 100, thereby changing the driving voltage of the LED module 160.
However, in the aforementioned dimming circuit, each of the first-stage AC-to-DC converting module 120 and the second-stage DC-to-DC converting sir module 140 has to work with a first control circuit 122 and a second control circuit 142 respectively, and adjusts and stabilizes its own outputting voltage through an additional feedback path. Thus, this design results in the problems of using more electronic components and having higher manufacturing cost. Further, because the two-stage driving circuit needs to undergo power conversion and voltage adjustment twice, the power conversion efficiency of the whole circuit is reduced.
In view of this, the aforementioned conventional dimming circuit is still inconvenient and deficient apparently, and needs further improvement. To solve the aforementioned problems, persons in the industry endeavor to search the solutions. However, a suitable dimming circuit is not completed for a long time. Therefore, how to simplify the LED dimming circuit and increase the overall power conversion efficiency is one of the important research topics, and is also a target that needs to be improved in the related fields.